An automatic transmission fluid (ATF) is oil that is used as a working oil of an automatic transmission. The ATF is not only used as a working fluid, but also used for lubricating and cooling.
However, the ATF has high viscosity in the early stage of cold start or in a low-temperature environment, so that power can be lost and fuel efficiency can be significantly reduced due to internal friction and line resistance. Further, a control valve, etc. may not likely to smoothly operate, and thus, a shifting shock or poor shifting is caused.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.